Carbon fiber-reinforced plastics (hereinafter, referred to as “CFRPs”), because of being lightweight and having excellent mechanical properties, have an impressive track record in the sporting materials such as golf club shafts, fishing rods and rackets as well as in the aircraft applications. In recent years, CFRPs have been increasingly applied also in the industrial fields of windmill blades, pressure containers, reinforcing construction materials and the like. Furthermore, in the automobile applications where the development of electric vehicles has been intensified and weight reduction is increasingly demanded, CFRPs are drawing much attention.
Conventionally, in CFRPs, because of the demand for high mechanical properties, thermosetting resins such as epoxy resins have been mainly used. However, in recent years, CFRPs using a thermoplastic resin that has a rapid processing cycle and excellent productivity have been actively studied. In particular, CFRPs in which polypropylene that is lightweight and inexpensive and has excellent water resistance and chemical resistance is used as a matrix resin (hereinafter, referred to as “thermoplastic CFRPs”) are expected to be widely used in the industrial applications.
Thermoplastic CFRPs generally assume the form of, for example, a compound pellet for injection molding or a sheet for stamping molding. In particular, a thermoplastic CFRP sheet using discontinuous fibers has excellent productivity and shapability and is thus a material form that attracts attention mainly in the industrial applications.